It is well known in the foundry industry to siphonically transport molten metal from one vessel to another. Siphons for this purpose comprise essentially a pipe having an inlet end submerged in the molten metal in a supply vessel and an outlet end submerged in the molten metal in a receiving vessel, wherein the surface of the metal in the receiving vessel is lower than the surface of the metal in the supply vessel. The vessels may have a variety of specific uses including such specific applications as furnaces, ladles, tundishes, launders, holding pots, and like typically found in a foundry.
Intrusion of air into a siphon is troublesome as it can "break" the siphon causing interruption in the flow of metal between the vessels, and it can react with the molten metal forming undesirable inclusions in castings formed therefrom. Because of its high reactivity, this later problem is particularly troublesome when handling molten aluminum.
Siphons have heretofore been made from refractory ceramic materials (e.g., ceramic-lined metal pipes). Refractory ceramics tend to be somewhat porous, and hence susceptible to the passage of air therethrough especially when a pressure drop exists between the inside and the outside of the siphon. Moreover, flowing metals, e.g., aluminum, are erosive and corrosive of both refractory ceramics and the typical metal pipes (e.g., cast iron) that encase them. Hence over time, siphons used heretofore develop air leaks which necessitate their frequent repair or replacement. Moreover, any joints that might be formed in multi-part siphons are likewise susceptible to air leakage for the same reasons as set forth above as well as may result from thermal expansion and contraction of the materials. It would be desirable to provide a siphon having a prolonged useful life and one which insures continuous metal flow of uncontaminated metal sufficient to complete a given pouring cycle once it has begun.
It has been suggested to mechanically raise and/or lower the height of a siphon pipe relative to the level of the liquid being siphoned to vary the flow rate of the liquid being siphoned. More typically however, in foundries at least, once the flow has been initiated the flow rate is not controlled, but rather determined only by the natural forces acting on the system such as the difference between the levels of the metal in the supply vessel and the receiving vessel, and the fixed height of the siphon above the level of metal in the supply vessel. It would be desirable to have a siphon which could be readily used to modulate the flow between one vessel and another.
It is a principle object of the present invention to provide a siphonic valve for controlling the flow of molten metal from one vessel to another which valve will continue to operate and deliver uncontaminated metal regardless of leakage of gas into the valve, and which is capable of readily turning on/off or modulating the flow of molten metal between the two vessels without introducing any contaminants into the metal. These and other objects and advantages of the present invention will become more readily apparent from the detailed description thereof which follows.